One known rotation transmission device which can selectively transmit rotation of a driving shaft to a driven shaft includes a two-way clutch and an electromagnetic clutch for selectively engaging and disengaging the two-way clutch.
The rotation transmission device disclosed in JP Patent Publication 2009-287724A includes an outer ring, an inner ring mounted inside the outer ring, and a control retainer and a rotary retainer each having bars mounted between the inner and outer rings such that the bars of the control retainer are arranged circumferentially alternating with the bars of the rotary retainer, whereby pockets are defined between circumferentially adjacent pairs of the bars of the respective retainers. The rotation transmission device further includes opposed pairs of rollers, each pair being mounted in one of the pockets, and elastic members mounted between the respective opposed pairs of rollers and biasing the respective opposed pairs of rollers away from each other toward stand-by positions where the rollers can instantly engage a cylindrical surface formed on the inner periphery of the outer ring and cam surfaces formed on the outer periphery of the inner ring, whereby when the inner ring rotates in either direction, one of each opposed pair of rollers engages the cylindrical surface and the cam surface, thereby transmitting rotation of the inner ring to the outer ring.
The rotation transmission device further includes an electromagnetic clutch mounted on an input shaft, which carries the inner ring. The electromagnetic clutch is configured to move the control retainer in the axial direction when the electromagnet of the electromagnetic clutch is energized. When the control retainer is moved in the axial direction by the electromagnetic clutch, the retainers are rotated relative to each other in the direction in which the circumferential widths of the pockets decrease due to the action of a torque cam provided between the opposed surfaces of a flange of the control retainer and a flange of the rotary retainer, whereby the pairs of rollers are moved by the bars of the respective retainers to the disengaged position, thus preventing transmission of rotation from the inner ring to the outer ring.
This rotation transmission device is further configured such that when the control retainer is moved by the electromagnetic clutch in the direction in which the flange of the control retainer moves away from the flange of the rotary retainer, the rotary retainer and the control retainer are rotated relative to each other under the biasing of the elastic members mounted between the respective opposed pairs of rollers, in the direction in which the circumferential widths of the pockets increase, thus allowing the rollers to instantly engage the cylindrical surface and the cam surfaces. Thus, when the rollers engage, the rollers move very little in the circumferential direction, so that the response of the clutch is good.
This rotation transmission device includes a spring holder rotationally fixed to the input shaft and kept in abutment with one end of the inner ring. The spring holder includes braking pieces (protruding pieces) on its inner periphery, with each braking piece having a spring support piece on its outer periphery which prevents radially outward movement of the corresponding elastic member. This arrangement stabilizes the positions of the respective rollers pressed by the elastic members, thus making it possible to reliably press the rollers toward the engaged positions. This in turn ensures reliable operation of the two-way clutch.
In the rotation transmission device disclosed in JP Patent Publication 2009-287724A, each spring support piece is formed with a through hole extending between both side surfaces thereof, and the elastic members, which are coil springs, are inserted in the respective through holes to prevent radial movements of the elastic members. With this arrangement, since the elastic members have to be inserted into the through holes in a direction perpendicular to the length direction of the bars, the bars tend to interfere with the elastic members when inserting the elastic members into the through holes. Thus, in order to avoid interference with the bars, the elastic members have to be inserted into the through holes while being bent in the length direction of the elastic members. It is therefore difficult to mount the elastic members in position, and it has been desired to more easily mount the elastic members in position.
This spring holder is rotationally fixed in position by the engagement between an engaging surface formed on the inner periphery of the spring holder and an engaging surface formed on the input shaft and opposed to the engaging surface of the spring holder. Thus, the spring holder keeps the control retainer and the rotary retainer in their respective neutral positions upon abutment of the bars of the two retainers against the side edges of the protruding pieces. However, since the bars of the two retainers tend to collide hard against the protruding pieces when the former abut the latter, and since there tends to be a slight time difference between when the bars of one retainer abut the protruding pieces and when the bars of the other retainer abut the protruding pieces, the (flat) engaging surface of the spring holder and the engaging surface of the input shaft, which are in engagement with each other to rotationally fix the spring holder, tend to be deformed or become damaged. Deformation of or damage to the spring holder could detrimentally influence the operation of the two-way clutch.
If the flat surface and/or the engaging surface is deformed, the spring holder may be moved axially due to looseness between the flat surface and the engaging surface. If the control retainer is inclined with the spring holder displaced axially, the edge on the inner periphery of the spring holder could engage the outer periphery of the input shaft and the spring holder could get locked to the input shaft. If the electromagnetic clutch is de-energized in this state, the spring holder interferes with the movement of the control retainer, making it impossible to move the control retainer to the predetermined engaged position. This makes it impossible to timely engage the two-way clutch. Thus, it is desired to reliably and accurately engage the two-way clutch of this conventional rotation transmission device.
In the rotation transmission device disclosed in JP Patent Publication 2009-287724A, while not shown, the two-way clutch and the electromagnetic clutch are entirely covered by a housing. Ordinarily in such an arrangement, a lead wire is connected to the electromagnetic coil of the electromagnet forming the electromagnetic clutch so as to extend to the outside of the rotation transmission device, and a male connector is connected to the distal end of the lead wire to which a female connector connected to the end of the power cord can be detachably connected.
In this arrangement, since the lead wire is exposed to the outside, when the rotation transmission device is mounted on an external device, the lead wire may get caught on an external part and be broken. The lead wire thus makes handling of the rotation transmission device difficult. It is desired to make handling of this rotation transmission device easier.